\(T_{s}\)  is governed by an underlying series of complex physical processes (see comprehensive reviews by [1]} & [2]} for detailed discussions on the different factors controlling \(T_{s}\) ). The observation of the cosmological signal is done through its contrast against the CMB - \(T_{s} >\)  \(T_{\gamma }\)  gives an emission signature and \(T_{s}<T_{\gamma }\)  gives an absorption signature wherein \(T_{\gamma }\)  is the CMB temperature.
